This invention relates to composite articles of vinyl resin compositions and fibers coated with an elastomeric coating.
Vinyl resin compositions are thermoplastics and can be molded for use in a variety of products. In some uses stiffness and strength, i.e., load bearing capability, are desired, and so the resins are reinforced with fibrous reinforcement materials to form a composite. Unfortunately, adding the fibers lowers the impact and crack resistance of the composite. Additionally, the adhesion between the resin and fibrous reinforcement can be undesirably weak. Thus, composites which are reinforced with fibers which will not have lower impact and crack resistance and in which there is good adhesion between the resin and the fibers are desired.
Polymers of lower molecular weight which are reactive are known in the art. For example, U.S. Pat. No. 4,133,957 describes amine-terminated liquid polymers represented by the formula ##STR1## wherein Y is a univalent radical obtained by removing hydrogen from an amine group of an aliphatic, alicyclic, heterocyclic or aromatic amine containing at least two secondary or mixed primary and secondary amine groups with no more than one primary amine group per molecule, and "B" is a polymeric backbone comprising carbon-carbon linkages. Other amine-containing liquid polymers having carbon-carbon linkage backbones and their uses are described in U.S. Pat. No. 4,221,885. The B. F. Goodrich Company markets a line of amine-terminated reactive liquid polymers under the trademark HYCAR.RTM. reactive liquid polymers.
Amine-containing polymers are also known which have carbon-oxygen linkages in the polymeric backbones. An example of this type of amine-containing liquid polymer is the polyether polyamines described in U.S. Pat. No. 3,436,359. Other examples of amine-containing liquid polymers having carbon-oxygen backbone linkages and their uses are described in U.S. Pat. Nos. 3,155,728; 3,236,895; 3,654,370; and 4,521,490. The '370 patent describes its amine-containing polymers as polyoxyalkylene polyamines. The '490 patent describes its amine-containing polymers as poly(oxyhydrocarbolene)diamines. The Jefferson Chemical Company subsidiary of Texaco, Inc. markets a line of amine-containing polymers under the Trademark Jeffamine.RTM. polyoxypropyleneamines.
Carboxyl-containing reactive polymers are also known in the art. For example, U.S. Pat. Nos. 3,235,589 and 3,285,949 describe carboxyl-terminated liquid polymers having a polymeric backbone comprising carbon-carbon linkages prepared by polymerizing dienes with or without vinyl nitriles and/or styrene in the presence of a bis-azocyanoalkyl acid initiator or an alkylene dicarboxylic acid peroxide. Carboxyl-containing polymers can also be prepared using the process described in U.S. Pat. No. 3,135,716 wherein monomers are polymerized using an organo-polyalkali metal compound to yield a polymer having a terminal alkali metal, and then post-reacting the polymer to form a terminal carboxyl group. The B. F. Goodrich Company markets a line of carboxyl-terminated reactive liquid polymers under the trademark HYCAR.RTM. reactive liquid polymers.
The above polymers share some common characteristics. All are of lower molecular weight, ranging from about 200 to about 10,000 number average molecular weight. In many cases, the polymers are liquids at room temperature (about 25.degree. C.). More importantly, all of the polymers are reactive, i.e. they can react, chain-extend, or cure with other chemicals, materials or polymers to form elastomeric or plastic solids. The above-referenced patents readily show and describe curing mechanisms and cure systems for the polymers. The reactive polymers can even co-cure with themselves as shown in U.S. Pat. No. 4,058,657. Often, the material used as a curative for the reactive polymers is an epoxy resin. For example, in addition to the above-mentioned patents, U.S. Pat. Nos. 3,316,185; 4,018,847; 4,055,541; 4,088,708; 4,119,592; 4,260,700; and 4,320,047 all show cures of reactive polymers using epoxy resins and other curing agents.
The reactive polymers are useful as components in castable systems, as tougheners or flexibilizers for epoxy and polyester resins in structural plastics, and in paints, coatings, sealants, adhesives, and the like.
The reactive polymers have been employed as impact or stress-fracture modifiers for brittle resins. In this work, they have been used in their pure liquid form or in the form of solutions. An example of such work is described in the book published by the American Chemical Society entitled "Rubber Modified Thermoset Resins" as part of the Advances in Chemistry Series, No. 208, edited by C. Keith Riew and John K. Gillham. Another reference on this subject is the article published in the ACS periodical, Rubber Chemistry and Technology, entitled "Amine-Terminated Reactive Liquid Polymers; Modification of Thermoset Resins" Vol. 54, No. 2, May-June 1981, by C. K. Riew.
The polymers can also be utilized in the form of a water-dispersion. One method that can be used to prepare water-dispersed compositions from liquid polymers involves mixing the polymer with water and soap using a high speed mixer such as an Eppenbach homogenizer or a Minisonic homogenizer. This process is not satisfactory as it introduces high levels of soap into the final composition.
A recent process has been developed to prepare water-dispersions of reactive polymers by first forming a "hydrophilic salt" of the polymer and then dispersing it in water. This process is described in copending applications Ser. Nos. 134,385 and 134,412, filed on Dec. 17, 1987. This process can be readily used as described therein or with minor variations to form water-dispersed compositions of amine-containing and carboxyl-containing reactive liquid polymers.
There have been attempts in the past at using reactive liquid polymers in forming films or coatings on substrates. When these polymers are used in their pure liquid form, uniformly thin films are not readily obtained. If the reactive polymers are used in the form of organic solutions, uniformly thin and continuous films are also not conveniently obtained. Further, the organic solvents are employed at high levels, over 90% and up to 99.5% by weight of the solution, which causes environmental and safety problems.
Another method of forming films on fibers is by electrodeposition or electropolymerization. In this method, a conductive fiber or a fiber with a conductive coating thereon is placed into an electrolyte solution containing electropolymerizable monomers. A current is applied and the monomers polymerize onto the fiber surface. An example of such a process is described in the article in Polymer Composites. February 1987, Vol. 8, No. 1, entitled "Application of Ductile Polymeric Coatings Onto Graphite Fibers" by J. P. Bell et al. A disadvantage of such a process is that the fiber must be conductive and the monomers employed must be compatible with the technique; i.e. electropolymerizable and dispersible in an electrolyte solution.
Also, reactive polymers have been used as impact modifiers, not in a "bulk" manner but as an elastomeric film on a reinforcing fiber. This work was first done and described in a February, 1985 Thesis by J. K. Kawamoto et al entitled "Impact Resistance of Rubber Modified Carbon Fiber Composite" published by the School of Engineering, Massachusetts Institute of Technology. In the study, a dilute solution (0.5% to 5.0% by weight) of a carboxyl-terminated poly(butadiene-acrylonitrile) liquid polymer in xylene was used to coat carbon fibers, which were then used to prepare epoxy composites which were tested for their impact strength and other properties. Although the study demonstrated the concept, a better process to achieve more uniformly thin and continuous coatings on fibers is desired.
Also, new composites of PVC which would have a combination of stiffness, impact resistance and crack resistance are desired and would be beneficial to the appliance and building materials industries.